More than a third of smokers reported having three or more dental problems, ranging from stained teeth to jaw pain, toothaches or infected gums. That was more than twice as much as people who never smoked.

But 20 percent of the smokers said they had not been to a dentist in at least five years. Only 10 percent of non-smokers and former smokers had stayed away that long, the study found.

Smokers seem to be aware their dental health is worse "but they're not doing anything about it," said Robin Cohen, a CDC statistician who co-authored the new report.

Why not? Half of the smokers said they could not afford to see a dentist, a much higher proportion than non-smoking adults who didn't go.

The report did not provide data on income or health insurance. But another CDC survey found smoking rates are higher among those with low incomes - nearly 30 percent of Americans with incomes below the federal poverty level say they are current smokers, while fewer than 19 percent of people with higher incomes are smokers.

A 2000 Surgeon General's report found that smoking can lead to poorer dental health by, for example, impairing the body's ability to fight off infections in the mouth. Tobacco use has also been associated with oral cancers.